I'm going to take issue with the "4 wheel lock up is shortest" comment, but on a theoretical vs practical basis.
The coefficient of sliding (locked-up) friction is much less than the coefficient achieved through a properly functioning contact patch, and as such, if it were possible to maintain absolutely perfect on-the-limit threshold breaking, that would produce shorter stops.
The fact that most drivers can't produce anywhere near that level is the reason that "locked up" is percieved to be better still exists.
And as stated above, ABS is a stability system, not a minimum-stopping-distance system, as it actually cycles the brake pressure, it doesn't attempt to hold a threshold condition.
And as for the thought of a bunch of untrained drivers consciously throwing their cars into uncontrolled broadslides... sheesh.